Newborn heart muscle grows back by itself, researchers find

Published 4:20 pm, Wednesday, March 9, 2011

In a promising science-fiction-meets-real-world story, researchers at UT Southwestern Medical Center in Dallas have discovered that the mammalian newborn heart can heal itself completely.

Researchers working with mice found a portion of the heart removed during the first week after birth grew back wholly and correctly, as if nothing happened.

"This is an important step in our search for a cure for heart disease, the No. 1 killer in the developed world," said Dr. Hesham Sadek, assistant professor of internal medicine and senior author of the study in the Feb. 25 issue of Science. "We found that the heart of newborn mammals can fix itself; it just forgets how as it gets older. The challenge now is to find a way to remind the adult heart how to fix itself again."

Previous research has demonstrated that the lower organisms, like some fish and amphibians, that can regrow fins and tails, can also regrow portions of their hearts after injury.

"In contrast, the hearts of adult mammals lack the ability to regrow lost or damaged tissue, and as a result, when the heart is injured, it gets weaker, which eventually leads to heart failure," Sadek said.

The researchers found that within three weeks of removing 15 percent of the newborn mouse heart, the heart was able to completely grow back the lost tissue, and looked and functioned just like a normal heart. The researchers believe that uninjured beating heart cells, called cardiomyocytes, are a major source of the new cells. They stop beating long enough to divide and provide the heart with fresh cardiomyocytes.

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Dr. Eric Olson, chairman of molecular biology and co-senior author of the study, said, "This work demonstrates that cardiac regeneration is possible in the mammalian heart during a window of time after birth, but this regenerative ability is then lost. Armed with this knowledge, we can next work to discover methods to reawaken cardiac regeneration in adulthood."

The next step, the researchers said, is to study this brief window when the heart is still capable of regeneration, and to find out how, and why, the heart "turns off" this ability to regenerate as it grows older.